Is repentance a one-time event, or do I need to repent each time I sin?

Psalm 51:16-17You do not desire a sacrifice, or I would offer one. You do not want a burnt offering. The sacrifice you desire is a broken spirit. You will not reject a broken and repentant heart, O God.

While salvation is a one-time event, God is pleased by a broken and contrite heart that is willing to continually confess and repent of sin.

1 John 1:8-9If we claim we have no sin, we are only fooling ourselves and not living in the truth. But if we confess our sins to him, he is faithful and just to forgive us our sins and to cleanse us from all wickedness.

Confession and repentance of sin is a constant mark of the person walking in the light of fellowship with God, keeping the relationship close and the lines of communication open.